"Of my own volition" = By my own WISH. "Of my own accord" = By my own AGREEMENT. These are Latin words. Actually wanting something and merely accepting it are not the same thing.

Both "of my own volition" and "on my own accord" mean that someone did something voluntarily, without being forced or influenced by others. However, there is a subtle difference in meaning between the two phrases: "Of my own volition" implies that the decision or action was made purely based on the individual's own will or desire. It emphasizes the person's personal agency and freedom of choice. "On my own accord" also suggests that the person acted voluntarily, but it may imply a sense of independence or self-reliance. It emphasizes that the person acted without help or assistance from others. So while both phrases convey a sense of voluntary action, "of my own volition" emphasizes the person's personal agency, while "on my own accord" emphasizes independence or self-reliance.

There's no difference in meaning at all. Each of them is another way to say "voluntarily."